1. Field of the Invention
This invention relates to an apparatus for detecting excess supply of the coolant circulated in a space cooling cycle of an automotive air conditioner or abnormal rise of pressure of the coolant and effecting a necessary measure such as sounding an alarm.
2. Description of Prior Art
Generally, space cooling cycles for automotive air conditioners are constructed as illustrated in FIG. 1. The space cooling cycle keeps a coolant circulated therein. The space cooling cycle comprises a compressor 1, a condenser 2 for causing the gaseous coolant which has been heated to an elevated temperature and compressed to an increased pressure in the aforementioned compressor 1 to be converted by cooling and condensing into a high-pressure liquid, a liquid tank 3 for depriving the coolant of moisture and dirt and effecting gas-liquid separation of the coolant, an expansion valve 4 for suddenly lowering the pressure of the coolant and consequently converting into a readily gasifiable low-pressure coolant, an evaporator 6 for evaporating the coolant and, owing to the thermal behavior of this evaporation, depriving the air in the car interior of its heat and consequently cooling the air in the car interior, and a temperature sensing tube 5 for sensing the temperature of the coolant at the outlet of the evaporator 6 and, in response to the temperature thus sensed, ajusting the opening degree of the expansion valve 4. The compressor 1 is driven by an automotive engine, though not illustrated, through the medium of a magnet clutch 8. When the temperature inside the car interior falls below a prescribed level, the magnet clutch is actuated to suspend the operation of the compressor 1 to prevent the car interior from being cooled excessively.
Since in the space cooling cycle of the automobile has its compressor driven by the car engine as described above, there is the possibility that the travelling condition of the car will alter the revolution number with which the compressor is driven and also alter the volume and pressure of the coolant circulated in the space cooling cycle.
The alteration of the volume of the coolant circulated may be moderated to some extent because the liquid tank 3 adjusts the flow volume of the coolant as occasion demands. When the space cooling cycle is not filled with a proper volume of the coolant, however, circulation of a proper volume of the coolant cannot be obtained in spite of the liquid tank 3. Particularly when the cycle is filled excessively with the coolant, the liquid tank 3 will be filled to capacity with the coolant in its liquid state, subcool of the coolant will also proceed within the liquid tank the coolant will retain a sparingly evaporable state even after passage through the expansion valve 4, and the coolant within the evaporator will fail to absorb heat sufficiently from the air. Thus, the space cooling cycle will fail to operate in its full capacity.
The aforementioned alteration of the pressure of the coolant occurs when the car speed is suddenly changed and consequently the revolution number with which the compressor is driven is abruptly altered. Especially when the pressure of the coolant is abnormally increased, there ensues the possibility that the temperature of the coolant will be elevated, the lubricant contained in the coolant will be degraded, and the cooling capacity of the cycle itself will be impaired.
To preclude the disadvantage, it has been customary for the liquid tank 3 to be provided in the upper portion thereof with a sight glass 7 as illustrated in FIG. 2 so that the flow condition of the coolant through the liquid tank 3 may be observed through the sight glass 7 and, on detection of insufficient supply of the coolant, the coolant may be properly replenished. In this case, bubbles observed in the coolant through the sight glass 7 serve as a visible sign of insufficient supply of the coolant. Absence of such bubbles, therefore, indicates proper supply of the coolant. The absence of bubbles in the coolant as observed through the sight glass does not exclusively occur when the supply of the coolant in the cycle is proper. It could occur when there is an excess supply of the coolant in the cycle. This special arrangement, therefore, has been unable to indicate accurately the excess supply of the coolant.
In another device proposed to date, the liquid tank 3 is provided with a high-pressure switch adapted to detect the pressure of the coolant, so that when the pressure of the coolant rises abnormally, this high-pressure switch will suspend the operation of the compressor and prevent the pressure of the coolant from rising abnormally. The high-pressure switch is capable of only detecting the abnormal rise of the pressure and is incapable of accurately sensing the excess supply of the coolant.
An object of the invention, therefore, is to provide a novel apparatus for warning abnormal coolant in the space cooling cycle.
Another object of this invention is to provide an apparatus for detecting excess supply of the coolant in the space cooling cycle of the automotive air conditioner and abnormal rise of pressure of the coolant and effecting a necessary measure such as sounding of an alarm, for example.